1. Technical Field
The present invention relates to a pickup device for use in an image forming apparatus, such as a printer, a copier, or the like, for picking up paper from a cassette and feeding the picked up paper to an image forming engine portion. More particularly, the invention relates to a pickup device for use in an image forming apparatus having a pickup unit for driving a pickup roller upward and downward in association with loading/unloading of the cassette.
2. Related Art
Generally, an image forming apparatus, such as a laser printer, a copier or the like, has a pickup device for sequentially picking up paper which is stacked or piled on a cassette detachably mounted in a main body of the image forming apparatus. The picked up paper is fed to an image forming engine portion.
A conventional pickup device of an image forming apparatus includes a hopper plate formed on the bottom of the cassette which is removable from the body of the image forming apparatus. The hopper plate is biased upward by a spring. Plural sheets of paper are loaded on the hopper plate in such a manner that an uppermost sheet of paper is in close contact elastically with a pickup roller. As a result of a rotational driving force of the pickup roller, the uppermost sheet of paper is fed to the image forming engine portion.
Accordingly, in the conventional image forming apparatus as described above, the cassette is usually loaded in or unloaded from the image forming apparatus in a direction corresponding to the direction in which the paper is fed and discharged. Therefore, front and rear ends of the image forming apparatus have to be large enough to permit loading or unloading of a cassette for accommodating large-sized paper.
To solve the above-described problem, the cassette can be loaded or unloaded through a side of the body of the image forming apparatus. However, in this case, jamming of the uppermost sheet of paper often occurs while mounting the cassette in the body of the image forming apparatus.
The present invention has been developed in order to overcome the above-mentioned problems of the related art. Accordingly, it is an object of the present invention to provide a pickup device for use in an image forming apparatus capable of picking up and feeding paper through upward and downward driving of a pickup roller in association with loading/unloading of a paper cassette.
Another object of the present invention is to provide a pickup device for reducing the volumetric appearance of the image forming apparatus by feeding the paper in a direction perpendicular to a paper cassette loading or unloading direction.
Yet another object of the present invention is to provide a pickup device capable of detecting and displaying information about the amount of remaining paper or lack of paper while picking up and feeding the paper from the paper cassette.
In order to accomplish the above objects, the invention provides a pickup unit for use in an image forming apparatus for picking up a sheet of paper from a stack or pile of paper loaded in a cassette which is detachably mounted in a body of the image forming apparatus. The paper is provided to an image forming engine portion. The pickup unit includes: a pickup roller for feeding an uppermost sheet of paper from the pile of paper on the cassette in a predetermined direction by contacting it, and thus transmitting a rotational driving force thereto; loading/unloading means for moving the pickup roller upward and downward in association with the loading/unloading of the cassette; and driving means for transmitting the rotational driving force to the pickup roller, thereby feeding paper from the cassette sequentially.
According to one aspect of the present invention, the loading/unloading means includes: a cam projection protruding from a leading end of the cassette; a supporting frame disposed on a cassette mounting portion of the body; a cam lever formed on the supporting frame and elastically biased in a predetermined direction so as to be interfered with, and thus pivoted by, the cam projection during the loading/unloading of the cassette; a pickup bracket disposed on the supporting frame, the pickup bracket having a free end which is moved upward and downward while rotatably supporting the pickup roller; an elastic body for elastically biasing the free end of the pickup bracket toward the cassette; and a locking arm connected with the cam lever so as to be operated in association with the cam lever for selectively locking/unlocking the pickup bracket.
According to another aspect of the present invention, the loading/unloading means includes locking/unlocking means for selectively restricting, and thus setting, the pickup bracket to be able to move upward and downward by manipulation of a main controller which is formed on the body irrespective of the loading/unloading of the cassette. The locking/unlocking means includes: a solenoid unit disposed on the supporting frame and controlled by the main controller; a rotary shaft disposed on the supporting frame and pivoted according to operation of the solenoid unit; and a hook member disposed on one end of the rotary shaft for selectively restricting, and thus locking/unlocking, the pickup bracket according to a pivoting movement of the rotary shaft.
According to yet another aspect of the present invention, the pickup unit includes paper remainder detecting means for detecting the remainder of the stack of paper, and for displaying detected information. The paper remainder detecting means includes: a paper contact lever moved upward and downward by the loading/unloading means to contact with the stack of paper on the cassette; a link arm pivoted in association with the paper contact lever, the link arm having a long hole formed in a body thereof; a guide portion disposed on the supporting frame and in parallel relation with respect to a side of the link arm, the guide portion having a guide slit overlapping a travel path of the long hole during a pivoting of the link arm; a slide pin restrictively connected in such a manner that it is passed through the long hole and the guide slit, said slide pin being linearly slid according to the pivoting of the paper contact lever and the link arm; and sensing means for detecting and outputting information about a displacement location of the slide pin in the form of a signal.